Simplify the following expression: $k = \dfrac{6tr + sr}{3sr + 6r^2} + \dfrac{tr + 6sr}{3sr + 6r^2}$ You can assume $r,s,t \neq 0$.
Solution: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{6tr + sr + tr + 6sr}{3sr + 6r^2}$ $k = \dfrac{7tr + 7sr}{3sr + 6r^2}$ The numerator and denominator have a common factor of $r$, so we can simplify $k = \dfrac{7t + 7s}{3s + 6r}$